Unfortunately, oils, hydraulic fluids, and other petroleum-based products almost inevitably leak onto pavement or other ground surfaces, eventually resulting in contamination of the environment. Much effort has been directed to avoiding such contamination. Since total containment of petroleum-based products may not be possible, efforts recently have focused on altering petroleum products to render those products less toxic to the environment. One promising approach has been to replace the base fluid--typically, a petroleum-derived hydrocarbon--with a vegetable oil, such as a naturally occurring or synthetic triglyceride or ester thereof. Vegetable oils are biodegradable, and thus environmentally friendly.
Unfortunately, triglycerides have poor low temperature viscometrics, and tend to congeal at temperatures below about -10.degree. C. (14.degree. F.). Many industrial fluids must have a pour point of less than -25.degree. C. (-13.degree. F.) and a Brookfield viscosity of 7500 to 110,000 centiPoise (cP) at -25.degree. C. (-13.degree. F.). In order for triglycerides to be used successfully as industrial base fluids, their low temperature viscometry must be improved.
A number of compounds are known to improve the low temperature viscometrics of vegetable oils. These compounds are known as "pour point depressants"(PPD's). Known PPD's for triglycerides include, but are not limited to: modified carboxy containing interpolymers; acrylate polymers; nitrogen containing acrylate polymers; and, methylene linked aromatic compounds. Unfortunately, known PPDs are not biodegradable. Therefore, the advantage in low temperature viscometry that is gained by using these PPD's is largely offset by the decrease in biodegradability of the resulting product. Also, manufacturing and environmental specifications limit the total amount of non-biodegradable material that can be used in a particular industrial fluid.
Biodegradable PPDs, which would meet the applicable specifications and not compromise the overall biodegradability of industrial fluids, are sorely needed.